The present invention relates to a laser with a laser medium which can be activated in at least two emission wavelengths, and which is arranged between two opposite plane-parallel and/or spherical mirrors and where one of the mirrors is partially permeable at at least one emission wavelength, and the other mirror totally reflects at least one of the emission wavelengths.
From the journal "Lasers and Applications", September 1984, pages 148ff, a neodymium-YAG laser is known, of which the emission wavelength can be switched between the values 1.06 .mu.m and 1.32 .mu.m. This is accomplished by means of optoelectronic means which are arranged between the laser medium and the totally reflecting mirror. The optoelectronic means consist essentially of a birefringent crystal and a Pockels cell. The "ordinary" ray of the birefringent crystal has the wavelength 1.06 .mu.m and the "extraordinary" ray with the lower intensity has the wavelength 1.32 .mu.m. By addressing the subsequent Pockels cell, the radiation is given a rotation of the direction of polarization of 45.degree. for each passage, so that a total phase shift of 90.degree. is brought about. Depending on the addressing, either the "ordinary" or the "extraordinary" ray can therefore travel through the birefringent crystal acting as a polarizer and for the respective other ray and therefore, for the respective other wavelength, the ray path remains blocked.